The patent gives the online retailer rights over the ability to buy a product online with the click of a single web page button.

It has caused controversy because opponents say that it is an obvious development that does not deserve patent protection. It is an example commonly cited by patent reform activists.

New Zealand actor Peter Calveley took the retail giant on, raising money from contributions to force the USPTO to re-examine the patent.

Calveley produced evidence that some of the innovation claimed by the patent was not new, called 'prior art' in patent law. Because of this the USPTO rejected 21 of the patent's 26 claims

Amazon submitted an amended version of the patent, narrowing its scope. The USPTO has now agreed to affirm the validity of this amended patent.

Though the scope of the patent is narrowed, the USPTO's affirmation of the patent is being seen by patent observers to indicate that the office is still prepared to back very broad patents covering inventions which many would think were simple or obvious.

"The approved-of amendment adds the seeming trivial limitation that the one-click system operates as part of a 'shopping cart model'," said Dennis Crouch, a respected patent blogger and law professor. "Because most retail eCommerce sites still use the shopping cart model, the added limitation appears to have no practical impact on the patent scope."

"I’m afraid that this case could become the poster-child for post-grant reform," he said.

Calveley said in his blog, though, that the changes that had to be made to the patent were important and will allow the technology to be used by others without fear of a patent suit from Amazon.

"Despite the Amazon corporate spin permeating the web, the amendment of the claims was significant and opens the way to the use of one-click shopping in a wide range of settings, and would be very useful, for example in mobile devices where people do not want to wade through a shopping cart," said Calveley in his blog.

Patents for technological developments which would be obvious to practitioners in that area of technology are not allowed in US law. Calveley said that the USPTO had not properly considered arguments that Amazon's claims were for an obvious development.

"The claim amendments were forced as I found prior art that clearly anticipated the claims. However the USPTO made no more than a cosmetic attempt to reexamine the claims from an obviousness perspective, despite the radically new prior art that was found," he said.

"The fact that 'one click shopping' is obvious from a common-sense viewpoint was what caused the public outcry in the first place, so one would think the USPTO would want to conduct a serious examination of this aspect rather than essentially ignoring it as they did," he said. "Therefore I am very glad that I had prior art that clearly anticipated their claims, rather than having to rely on obviousness."